The present invention relates to control systems for internal combustion engines, and more particularly to control systems that estimate torque for engine RPM and torque control.
Conventional control systems that estimate torque are predominantly designed to control shift quality. The torque-estimating accuracy of these systems is defined by the desired quality for transmission shifts. Torque estimation calculations are based on the following relationships:
IndTorque=k*GPO*Ncyl*EFF*Ncylxe2x80x94shutxe2x88x92SparkLoss
FrictionTorque=BaseTable*OTcorrector+ACCdriveFriction
Torque=IndTorquexe2x88x92FrictionTorquexe2x88x92InertiaTorque
where GPO is mass air flow (gram of air per cylinder), Ncyl is a total number of cylinders in the internal combustion engine, EFF is a function of the air/fuel ratio, sparkloss is a function of RPM and GPO, and OTcorrector is an oil temperature correction.
The conventional torque estimation systems do not have direct inputs such as RPM, exhaust gas recirculation (EGR), spark, and other inputs that are needed for engine RPM and torque control (ERTC). The conventional torque estimation systems are also unable to recalculate inputs based upon requested torque or to optimize brake torque.
An engine toque estimator according to the invention includes a vehicle data bus that provides a plurality of engine operating parameters including at least one of engine RPM, spark and dilution estimate signals. A steady state torque estimator communicates with the vehicle data bus and generates a steady state engine torque signal. A measurement model communicates with the vehicle data bus and compensates for errors that are associated with engine manufacturing variations. A dynamic torque estimator communicates with at least one of the vehicle data bus, the measurement model, and the steady state torque estimator and generates an actual engine torque signal.
In other features of the invention, the engine-operating inputs further include air per cylinder, unmanaged spark, oil temperature, air/fuel ratio, barometer, enabled cylinders, and intake air estimate signals. The steady state torque estimator generates at least one of a GPO sensitivity signal, an RPM sensitivity signal, a spark sensitivity signal, and a spark squared sensitivity signal. The steady state torque estimator further generates an unmanaged engine torque signal. The steady state torque estimator outputs a steady state engine torque signal to the dynamic torque estimator. The measurement model outputs a torque estimate correction signal to the dynamic torque estimator. The dynamic torque estimator outputs the actual engine torque signal.
In yet other features, the steady state torque estimator includes a base steady state torque calculator, a steady state torque temperature corrector, and a steady state torque air/fuel corrector. The base steady state torque calculator receives the RPM, spark, unmanaged spark, dilution estimate and GPO signals from the vehicle data bus and generates the GPO, RPM, spark, and spark squared sensitivity signals. The base steady state torque calculator generates a base unmanaged engine torque signal that is output to the steady state torque temperature corrector. The steady state torque temperature corrector receives oil temperature and GPO signals from the vehicle data bus and generates a steady state unmanaged torque base signal that is output to the steady state torque air/fuel corrector. The steady state torque air/fuel corrector generates unmanaged engine torque and steady state engine torque signals.
In still other features, the base steady state torque calculator includes a torque sensitivity calculator and a final base steady state torque calculator. The torque sensitivity calculator receives the dilution estimate and RPM signals from the vehicle data bus and generates the GPO, RPM, spark, and spark squared sensitivity signals. The sensitivity signals are input to the final base steady state torque calculator. The final base steady state torque calculator receives the GPO, RPM, spark and unmanaged spark signals from the vehicle data bus. The final base steady state torque calculator calculates base steady state unmanaged torque and base steady state torque signals.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.